Biological photovoltaics (BPV) is an energy-generating technology which uses oxygenic photoautotrophic organisms, or fractions thereof, to harvest light energy and produce electrical power. In contrast to microbial fuel cells which generate electricity from the metabolic process of living microbes, biophotovoltaics produce electricity from light energy via light harvesting apparatus of photosynthetic organisms.
Algae are amongst the most efficient photosynthetic organisms with fast growth rates and tolerance in extreme environments. Nishio et al. (2010) proposed that it is likely that green algae and heterotrophic bacteria grew in the anode biofilm and formed layered structure. It was suggested that green algae and cyanobacteria cooperatively converted light energy into electricity.
Further, McCormick et al. (2011) disclosed a mediatorless biophotovoltaic system by virtue of using bacterial species capable of self-mediated extracellular electron transfer. Particularly, green algae or cyanobacteria strains were grown directly on an indium tin oxide-polyethylene terephthalate (ITO-PET) on anode in a sandwich type or an open air design BPV system. Besides, Ng et. al (2013) disclosed suitable strains of algae capable of forming biofilm on ITO and glass anode in a BPV device for electric power generation. Photosynthetic efficiency of the biofilms were determined.
It appears that anode material is crucial in determining power outputs in a BPV system. In this aspect, Bombelli P. et al. (2012) disclosed their study relating to surface morphology and surface energy of anode material including ITO-PET, stainless steel, glass coated with a conductive polymer and carbon paper. Apart from choosing a suitable anode material, method of treating anode for better adherence of biofilm derived from green algae or cyanobacteria was crucial in enhancing efficiency and power output of a BPV system. The abovementioned thin film or slides of ITO are usually formed via physical vapour deposition on solid surfaces. Particularly, they can be obtained by electron beam evaporation or sputter deposition technique. As such techniques are required to be conducted under vacuum condition, the production of the ITO thin film or slides requires skilled workmanship and specialized facilities hence lead to high production cost.
As an alternative, carbon-based films, such as films of graphene are highly sought-after due to its transparency and relatively lower electrical resistance properties comparing to ITO. The present invention provide method of preparing electrode with such a carbon-based biofilm and BPV device thereof.